#include <stdio.h>
#include <unistd.h>

int main()
{
    printf("I am running ...\n");
    pid_t id = fork();
    if(id == 0) // child
    {
        while(1)
        {
            printf("do something\n");
            sleep(1);
        }
    }
    else if(id > 0) // parent
    {
        while(1)
        {
            printf("call child, do something\n");
            sleep(2);
        }
    }
    else 
    {
        // fork error!
    }

    return 0;
}
